CBB9M
23 year Ranger veteran
Joined: Sun Oct 22nd, 2017
Posts: 371
Name: Bill ... Occupation: Interests:
Reputation Points: 371
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Round two (because trying to edit a post and you can't see what your tying absolutely sucks)....Ford temp display modules of the mid 90's-200X vintage that people are talking about in these forums use the conditioned vehicle speed signal (ie, square wave) to indicate to the device (could as an example be EATC, as I know well) that the vehicle is or is not moving. The reason these modules need and use this signal is because, when the is/is not not moving and the outside temperature drops, the module will update at a rate of every few seconds until the correct temperature is reported. When the outside temp goes up AND the module does NOT get a valid speed signal, the module updating frequency defaults to increasing (upping) the reported temperature at the rate of 1*F every 20 minutes (personally tested OHC module behavior and response to temp increase and decrease with and without a speed signal). The correct reason for decreasing the rate of increasing temp updates when a vehicle is stopped and in a correctly working system, as evidenced by various Ford TSB's, is to lessen/eliminate false temperature readings caused when the vehicle is stopped (stoplight for example) and conditions that would cause a false temp reading exist (ie and for example, radiation heat transfer between a scorching hot black radiator/black asphalt/black car and your black temp sensor). If you do not wire the speed signal to the module, then what happens is the module, in absence of the speed signal, defaults to increasing the temperature at the rate of 1*F every 20 or so minutes. If you back out of your 70* garage on a 90* day, park in a underground parking garage somewhere then leave, park in a cool shady area then drive away, or any other condition where the correct temp reported needs to be done in a way that it can be increased at a rate faster than 1*F every 20 min, and it can't, then you will be looking at a bogus temp being reported. Last edited on Sat Dec 2nd, 2017 11:39 am by CBB9M
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-Bill
04 Ranger FX4 Level II, several mods
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